Menelik Watson whipped his massive right arm toward the left shoulder of Garett Bolles and quickly gauged the technique and instincts of the Broncos’ first-round draft pick.

The offensive tackles, both in their first training camp with the Broncos, repeated the makeshift drill for several minutes during a break in practice Friday, a lesson on the fly between two of what could be as many as four new starters on the team’s offensive line.

Later, after the double blast of an air horn signaled the end of the morning practice, veteran guards Ron Leary and Allen Barbre walked off the field in perfect matching strides.

Whether the four new linemen can create similar chemistry when the season begins is a question that may reside at the center of the Broncos’ quest for offensive improvement.

“That’s the million-dollar question,” said Barbre, 33, who was traded to Denver by the Philadelphia Eagles on Wednesday. “If we come out here every day and work hard, we’re one step closer every day.”

The Broncos aimed to add toughness to their offensive line in March with the free-agency acquisitions of Leary and Watson, who started Friday’s practice on the right side of the first-team line, with center Matt Paradis, guard Max Garcia and the tackle Bolles filling out the line to Leary’s left. First-team repetitions, though, were rotated constantly throughout the practice.

Leary joined the Broncos after helping the Dallas Cowboys form one of the best offensive lines in the NFL last season. Watson was signed a day later, bolstering the tackle position after spending the previous four seasons with the Oakland Raiders….